Method for evaluating the mechanical performances of a switchgear apparatus

ABSTRACT

A method for evaluating mechanical performance of a switchgear device having at least one pole which includes a pair of contacts movable between open and closed positions, a support arm of a first contact, a support arm drive including a rotary pole shaft and a rod pivotably coupling the drive to the support, an energy storage system for moving the arm to close the contacts, and a toggle device with a trip latch, the method including measuring the angle of rotation of the pole shaft during contact closing, deriving specific values by measuring the angle of rotation, comparing the values with an initial reference value, identifying wear performances of the drive by comparing the specific values with the reference value, determining on a variation curve of the angle of rotation versus time, a first specific time to reach a first inflection point when the pole shaft reaches a maximum speed of rotation, and a second time to reach a point on the curve at a theoretical final angle of rotation when the contacts are closed, calculating the elapsed time between the first and second times, and deriving an excess energy level of the energy storage system as a function of the difference between the calculated elapsed time and a theoretical value.

BACKGROUND OF THE INVENTION

The invention relates to a method for evaluating the mechanicalperformances of a switchgear apparatus comprising at least one pole.Each pole comprises a pair of main contacts movable with respect to oneanother between an open position and a closed position. A drivemechanism of a support arm of a first main contact comprises a rotarypole shaft and at least one rod coupling the drive mechanism to thesupport arm in pivoting manner. Said mechanism comprises an energystorage system designed to cause movement of said arm to place the maincontacts in a closed position.

The invention also relates to a switchgear apparatus for implementationof said method.

STATE OF THE ART

A power supply line of an electric load to be controlled isconventionally provided with at least one switchgear apparatus which,for each phase, comprises pairs of contacts movable with respect to oneanother to switch the load. Actuation of the contacts can be performedin different manners; in particular, for certain high-power switchgearapparatuses (in particular more than 600 A), used for example for safetypurposes as line incomer, a high electrodynamic strength is required andthe contacts are driven by a lever system coupled to a rotary spindle,itself actuated by a toggle mechanism with two pivoting rods, asdescribed for example in EP 0,222,645, EP 0,789,380 or EP 1,347,479.

One cause of malfunctioning of known switchgear apparatuses concerns thetoggle actuating mechanism described above. This actuating mechanismalso called OCO (open-closed-open) mechanism, is moved by aspring-loaded mechanical actuator. This spring-loaded mechanism alsocalled “grenade” mechanism is thus used to perform closing of thecircuit breaker. This “grenade” mechanism provides the necessary energyfor the OCO mechanism and also enables an operator to perform operationson the switchgear apparatus in total safety. Use of the latter does infact limit the risks of exposure linked to the presence of an electricarc in case of incorrect closing. The circuit breaker generallycomprises a motor for resetting the “grenade” mechanism. Said motor isactuated as from the end of the closing phase of the OCO mechanism toset the “grenade” mechanism.

This “grenade” mechanism can present operating faults in the course ofits use in time. A decrease of the energy performances of the “grenade”mechanism is liable to be responsible for incomplete closing of the OCOmechanism. The reasons for malfunctioning of the “grenade” mechanism aremultiple. They can in particular be related to a loss of stiffness ofthe springs of the “grenade” mechanism, an increase of the mechanicalfrictions of the kinematic chain of the different moving parts in thecircuit breaker, or an increase of the resistive torque on the bar ofthe circuit breaker.

If the action of the “grenade” mechanism is not sufficient to operatethe OCO mechanism, the switchgear apparatus can nevertheless be in aclosed position while at the same time not being latched. The toggle ofthe OCO mechanism does in fact unfold due to the action of the “grenade”but does not overshoot its operation dead point. The circuit breaker isthen closed while not being latched and can have a current flowingthrough it. In the latter position, the “grenade” mechanism performsholding of the OCO mechanism in a closed position, whereas in operationcalled “normal operation”, the OCO mechanism has to latch in autonomousmanner on a stop. In the particular case of the embodiment described,the toggle mechanism passing the dead point brings the OCO mechanism upagainst a stop in the closed position. If the switchgear apparatus is ina closed non-latched state and the resetting motor is actuated, thecircuit breaker is then in a phase called slow opening phase, a phasewhich is totally prohibited. Indeed, as the OCO mechanism is no longersecured by the “grenade” mechanism during resetting, said OCO mechanismtends to open in spontaneous manner. An electric arc can then occur andrepresent a risk for the circuit breaker causing “explosion” of thelatter.

SUMMARY OF THE INVENTION

The object of the invention is therefore to remedy the shortcomings ofthe state of the art, so as to propose a diagnostic method forevaluating the mechanical performances of a switchgear apparatus, inparticular of the spring-loaded mechanism performing closing of the OCOactuating mechanism.

The method according to the invention consists in measuring the angle ofrotation of the pole shaft during a closing time of the contacts and inreconstituting at least two specific values from the measurements. Saidspecific values are then compared with a specific initial operatingreference of the switchgear apparatus to diagnose the mechanical wearperformances of the drive mechanism according to a comparative statebetween the specific values obtained and those of the operatingreference.

According to a preferred embodiment of the invention, the methodconsists in determining a first specific value equal to a first timenecessary to reach a first inflection point on a curve of the variationof the angle of rotation. Said inflection point corresponds to themoment when the pole shaft reaches a maximum speed of rotation. A secondspecific value equal to a second time necessary to reach a point on thevariation curve is determined. This second point corresponds to atheoretical final angle of rotation reached when the pair of contacts isin a closed position. The elapsed time between the first and secondtimes is calculated to diagnose an excess energy level of the energystorage system of the drive mechanism according to the differencebetween the value of the calculated elapsed time and a theoreticalvalue.

According to a particular embodiment of the invention, the methodconsists in determining a third specific value on a curve of thevariation of the angle of rotation corresponding to a time to reach afirst local maximum on the variation curve. Said first local maximumcorresponds to the maximum angle of rotation reached by the pole shaftin the course of closing. A fourth specific value on the variation curveof the angle of rotation is determined and corresponds to a final angleof rotation reached when the pair of movable main contacts are in aclosed position. The angular difference between the maximum angle ofrotation and the final angle of rotation is calculated to diagnose alatching state of a toggle device of the drive mechanism of the poleshaft according to said angular difference.

The switchgear apparatus for implementation of the method as definedabove comprises a pair of movable contacts able to move with respect toone another between an open position and a closed position. A drivemechanism of the support arm of a first contact comprising a rotary poleshaft and at least one rod couple the drive mechanism in pivoting mannerto the support arm. An energy storage system is provided to causemovement of said arm to place the main contacts in a closed position.The switchgear apparatus comprises a plurality of identical poles and apole shaft common to all the poles, the pole shaft being the rotaryspindle of the drive mechanisms.

Preferably, the support arm comprises a first part supporting the firstcontact and a second part, the two parts sliding with respect to oneanother so that, in the closed position of the pair of contacts, thesecond part can take a first abutment position and a secondend-of-travel position in which the first part is sunk into the secondpart.

According to a mode of development of the switchgear apparatus, thedrive mechanism of the pole shaft comprises a resetting device having anenergy storage system with a flexible device comprising at least oneclosing spring to move the movable contact to the closed position,loading of the closing spring being performed by a resetting cam drivenin rotation by means of a manual lever or a servomotor.

Preferably, the drive mechanism of the pole shaft comprises a toggledevice associated with a trip latch and with an opening spring to movethe support arm of the movable contact, the device comprising two rods.

The switchgear apparatus comprises means for determining the angle ofrotation of the pole shaft, said means comprising a rotation sensor acomponent of which is arranged on the pole shaft.

According to a particular embodiment, the rotation sensor comprisesmagnetic means arranged on the axis of rotation and detection meansfitted on the case of the switchgear apparatus, the magnetic means andthe detection means communicating without any contact.

According to a particular embodiment, the rotation sensor comprises acog-wheel arranged on the axis of rotation and detection means fitted onthe case of the switchgear apparatus, the cog-wheel and the detectionmeans communicating without any contact.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from thefollowing description of particular embodiments of the invention, givenfor illustrative and non-restrictive example purposes only andrepresented in the appended drawings.

FIG. 1 illustrates a switchgear apparatus for implementation of themethod according to the invention;

FIG. 2 represents a detailed perspective view of the actuating mechanismof a switchgear apparatus according to FIG. 1;

FIG. 3 represents another detailed perspective view of the actuatingmechanism of a switchgear apparatus according to FIG. 1;

FIG. 4 represents a detailed perspective view of the rotation sensor ofa switchgear apparatus according to FIG. 1;

FIGS. 5A-5E show an actuating mechanism according to FIG. 2 in thecourse of the closing steps;

FIG. 6 represents a sensor used in a particular embodiment of theinvention;

FIG. 7 represents a curve of the variation of the angle of rotation ofthe contact-support pole shaft of the actuating mechanism in the courseof closing.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIG. 1, a switchgear apparatus 10 for high currents,above 600 A, in conventional manner comprises a pair of electriccontacts 12, 14 for each pole. Each electric contact is preferablyassociated with a pad made from suitable material, for example asilver-based alloy. One of the contacts 14 is fitted on an arm 16 ableto pivot between an open position in which it is separated from thestationary contact 12 and a closed position in which mechanical andelectric contact between the contacts 12, 14 is established. The polealso comprises an arc extinguishing chamber 18 and a pair of mainterminals (not illustrated) designed to connect onto connection strips.For these high ranges, the switchgear apparatus 10 comprises a pluralityof poles arranged in parallel planes, perpendicular to a pole shaft 20which is common to the poles: the closing or opening order of the polesis transmitted to each movable contact 14 from the pole shaft 20 bymeans of a drive mechanism 22 with a lever (FIG. 2).

The pole shaft 20 is mounted rotating on the case of the switchgearapparatus 10 and is actuated by suitable means. In particular, for openswitchgear apparatuses 10 with an intermediate pole shaft 20 and highelectrodynamic strength, the drive mechanism 22 is of the toggle typewith two rods 24, 26 pivoting with respect to one another. One of therods 24 is articulated in rotation on a trip latch 28 mounted pivotingon a fixed spindle; the other rod 26 is mechanically coupled to a crank30 of the pole shaft 20, which is also common to the set of poles andfurther forms one of the levers of the drive mechanism 22 of theelectric contacts.

An opening spring 32 is anchored between the crank 30 and a fixedsecuring pin, and biases the crank 30 to its open position. An openingratchet 34, formed by a lever pivoting around a fixed spindle, iscontrolled by an opening latch 36 in the shape of a half-moon. Theopening ratchet 34 is biased by a spring towards the trip latch 28,moving away from the half-moon 36. A roller is arranged on the openingratchet 34 between the ends of the latter to collaborate with a V-shapedrecess of the trip latch 28, which is biased by a spring (not shown)tending to shorten the distance between the articulation axis of thetoggle mechanism 24, 26 on the trip latch 28 and the articulation axisof the toggle mechanism on the crank 30.

In a preferred embodiment, the switchgear apparatus 10 is able to bereset, i.e. it is provided with energy storage means so as to assist theclosing function, such as for example a “grenade” mechanism as describedin the document EP 0,222,645. In particular, a drive lever 40 is mountedpivoting around a fixed spindle 42, and a flexible energy storage devicecomprising at least one closing spring 44 is mounted pivoting on a fixedpoint and on a finger of the drive lever 40. The drive lever 40 supportsa roller 52 designed to collaborate with a loading cam 48 keyed onto ashaft 50. The roller 52 is designed to collaborate with a closingratchet 54 pivoting around a fixed spindle. A closing latch 56, designedto latch the ratchet 54, is flexibly biased by a spring to its closedposition; the ratchet 54 is itself biased by a spring to its latchedposition.

The pole shaft 20 is actuated by means of these different elements andthen drives the movable contacts 14. For this purpose, its crank 30 isprovided with a connecting rod 60, for each pole, which connects it tothe support arm 16 of the movable contact 14. The support arm 16 isprovided with two parts sliding with respect to one another: a pole cage62 is moved directly by the rod 60 with respect to which it is pivotallymounted. The part 64 of the arm 16 which bears the contact pad 14 slidesinside the pole cage 62, preferably in articulated manner around aspindle 66. Means forming a spring 67, for example one or more contactpressure springs, arranged between the support 64 and the pole cage 62,urge the pad 14 to the salient position with respect to the cage. Thisconfiguration enables a closing over-travel of the contact pad 14 withrespect to abutment, so that in the position in which the current isflowing between the contacts 12, 14, the pole cage 62 can continue itsmovement without accentuating the pressure on the contacts pads 12, 14.The arm 16 is thus pivotally mounted via its cage 62 around a firstspindle 68 between the closed position and the open position, and thesupport 64 of the movable contact 14 is articulated on a second spindle66 of the pole cage 62.

When closing of the contacts 12, 14 takes place, in a first stage, thepole shaft 20 is therefore made to rotate, and the toggle mechanismdrives the contact arm 16 directly. On closing, the two contact pads 12,14 come into contact. The shaft 20 can then continue its travel, andmovement of the pole cage 62 of the arm 16 continues beyond the abutmentposition, the movable contact 14 “sinking” into the pole cage 62.

Furthermore, in the illustrated embodiment, the toggle system 24, 26connected to the offset pole shaft 20 enables the movements to begeared-down. Travel of the pole shaft 20 in rotation continues over alarge angle θ₂ after closing of the poles. In particular, the totaltravel θ_(final) of the pole shaft 20, which is fixed and determined bythe design of the apparatus, is about 50 to 55°. At mid-rotation of theshaft 20, the movable contact 14 has already covered ¾ of its travel,and the opening of the contacts is only 10 mm. Therefore, when abutmentof the contacts 12, 14 takes place and after a travel θ₁, the shaft 20preferably still has about 30% of its rotation to perform.

According to the invention, a sensor 70 measures the rotation of thepole shaft 20 between the beginning of movement of the pole shaft 20 andthe end of travel of said shaft 20. End of travel of the pole shaft 20corresponds to the closed position of the electric contacts. The sensor70 also measures the rotation θ of the pole shaft 20 between the momentabutment between the movable and stationary contacts 12, 14 takes place,i.e. the beginning of current flow in the device 10, and the end oftravel of the shaft 20 in the closed position.

The method for evaluating the mechanical performances of a switchgearapparatus according to the invention comprises the following successivesteps.

A first step consists in measuring the angle of rotation θ of the axisof the poles 20 during closing of the movable main contacts 12, 14 bythe drive mechanism 22.

A second step consists in reconstituting at least two specific valuesfrom the measurements made in the previous step.

According to a preferred embodiment of the invention, the methodconsists in determining a first specific value equal to a first time T₀necessary to reach a first inflection point A on a curve S_(θ) of thevariation of the angle of rotation θ (FIG. 7). Said inflection pointcorresponds to the moment when the pole shaft 20 reaches a maximum speedof rotation. As represented in FIG. 7, the pole shaft 20 has performed arotation through an angle θ₀. As represented in FIG. 5C, the firstinflection point A also corresponds to the moment when the electriccontacts 12, 14 come into contact.

The variation of the value of the angle at the moment when the electriccontacts 12, 14 come into contact gives an indication on the wear of theswitchgear apparatus. No-load and on-load operations of the apparatus infact cause wear of the contact pads, whether they be those of thestationary or movable contacts. Removal and crushing of material thatresults therefrom delays coming into contact of the poles and can resultin an increase of the value of the first time T₀.

The method consists in determining a second specific value equal to asecond time T₁ necessary to reach a second point B on the variationcurve S_(θ) of the angle of rotation θ. Said second point corresponds toa theoretical final angle of rotation θ_(final) reached when the pair ofmovable main contacts 12, 14 is in a closed position. This theoreticalreference value of the final angle of rotation is preferably a productcharacteristic linked to the switchgear device. This characteristic isthen provided by the manufacturer. This reference value can also beestimated following a sequence of measurements performed when theapparatus is new. The reference value is recorded so as to besubsequently used in the method according to the invention.

A third step of the method consists in comparing said specific valueswith theoretical values extracted from a specific initial operatingreference of the switchgear device. According to a preferred embodiment,the method consists in calculating the elapsed time ΔT between the firstand second times T₀, T₁. This elapsed time between the first and secondtimes T₀, T₁ is then compared with a reference value representative ofoperation of a non-worn switchgear apparatus.

This reference value is established according to the “mechanical”configuration of the switchgear apparatus: number of poles, springs ofthe grenade, and recorded in the information processing module to beused and compared according to the constitution of the switchgearapparatus. This reference value is preferably a product characteristiclinked to the switchgear device. This characteristic is then provided bythe manufacturer. This reference value can also be estimated following asequence of measurements performed when the apparatus is new. Thereference value is recorded so as to be subsequently used in the methodaccording to the invention.

A last step of the method for evaluating the mechanical performances ofa protection apparatus consists in diagnosing certain mechanicalperformances of wear of the drive mechanism 22 according to acomparative state between the determined specific values and thereferences values provided by the operating reference. According to apreferred embodiment, the method according to the invention consists indiagnosing an excess energy level of the energy storage system of thedrive mechanism 22 according to the difference between the value of theelapsed time calculated with respect to the theoretical reference value.

In other words, the last step of the method according to the inventionprovides information on the energy reserve available in the grenade toperform closing: the excess energy. If the resistive forces increase,this energy reserve decreases and the angular travel of the pole shaft20 from the time when the electric contacts 12, 14 come into contact(inflection point A) is increasingly slowed down. The difference ΔTbetween the value of the elapsed time calculated with respect to thereference value also tends to increase with wear of the switchgeardevice in the course of use of the latter.

According to a particular embodiment of the invention, the method forevaluating consists in determining a third specific value C on a curveS_(θ) of the variation of the angle of rotation θ corresponding to thetime T_(max) to reach a first local maximum C on the variation curveS_(θ). As represented in FIG. 5D, said first local maximum C correspondsto the maximum angle of rotation θ_(maxi) reached by the pole shaft 20in the course of closing.

This step corresponds to passage of the top dead point of the toggledevice 26, 24 of the drive mechanism 22. After this step, it is nolonger the drive lever 40 that pushes the drive mechanism 22, but thepole springs 67 which, by return of force, bring the toggle device 26,24 to bear on the trip latch 28. A variation of the maximum value of theangle of rotation θ_(maxi) gives us an indication of the wear of thedrive mechanism 22.

The method, according to this particular embodiment, then consists indetermining a fourth specific value (point D) on the variation curveS_(θ). This fourth specific value (point D) corresponds to a finalmeasured angle of rotation θ_(final) reached when the pair of movablemain contacts 12, 14 are in a closed position.

In a following step, the angular difference Δθ between the maximum angleof rotation θ_(maxi) and the final measured angle of rotation θ_(final)is calculated. Determination of this angular difference enables alatched state of the toggle device 26, 24 of the drive mechanism 22 tobe diagnosed. Indeed, if the calculated angular difference Δθ is higherthan a threshold, in other words if the maximum angle of rotationθ_(maxi) is greater than the measured final angle of rotation θ_(final),then the toggle device 26, 24 is latched after it has correctly passed atop dead point (FIG. 5D). If the calculated angular difference Δθ isgreater than said latching threshold, the switchgear apparatus is in alatched closed state. The latching threshold corresponds to acharacteristic provided by the manufacturer. This characteristiccorresponding to the latching threshold can also be estimated followinga measuring sequence performed when the apparatus is new. Thecharacteristic is recorded in order to be subsequently used in themethod according to the invention.

From the time the electric contacts 12, 14 come into contact (firstinflection point A), movement of the drive mechanism 22 causescompression of the contact springs 67 comprised between the pole cages62 and the supports 64 of the movable contacts 14. This compression,which is expressed by contact depression, conditions the pressure forcewhich will be exerted on the electric contacts 12, 14 in the closedposition. This pressure force also defines the electro-dynamic strengthof the switchgear apparatus.

According to a first embodiment, the sensor 70 is preferably located onthe pole shaft 20 outside the areas liable to be polluted by debris whencurrent interruptions take place and far away from any possibleprojections of hot gases. Switchgear apparatuses 10 with highelectrodynamic strength have a lifetime of up to thirty years;advantageously, the sensor 70 is of the contact-free type in order tolimit any skew due to wear or friction within the sensor 70.

As represented in FIGS. 3 and 4, the rotation sensor 70 comprises acog-wheel 112 or a portion of cog-wheel arranged on the pole shaft 20.In another embodiment that is not represented, the wheel is formed by asuccession of magnetic poles. Detection means 114 such asmicroelectronic devices implementing sensitive elements of inductivetype, Hall effect cells, or magneto-resistance cells, are fitted on thecase of the switchgear apparatus 10, facing the cog-wheel or themagnetic poles. The cog-wheel 112 and detection means 114 communicatewithout any contact. The detection means 114 preferably incorporatenumerical processing means of the analog signals generated by passage ofthe teeth of the cog-wheel or passage of the magnetic poles, to give anumerical transcription thereof in the form of two square signals offsetby a quarter of a period. In certain types of embodiment, the detectionmeans can integrate interpolation functions of the analog signals.

According to a second particular embodiment that is not represented, thesensor 70, of small volume, is preferably located at the end of the bar20, for example at an end close to the case of the switchgear apparatus10. A sensor of magnetic type without sliding contact, in particular amagnetic array type rotation sensor, is particularly suitable due to itsabsence of parts liable to wear quickly. As illustrated in FIG. 6, thistype of sensor 70 comprises magnetic means 72, in particular a magnet,which can be secured to the element whose rotation is to be determined;in particular, the magnet 72 can be directly coupled on the pole bar 20by sticking at its end, or any other mechanical means. The sensor 70further comprises detection means 74, and in particular a detector ofprinted circuit card type with sides of about 4 mm. The detector 74 ispositioned facing the magnetic means 72, for example coupled to the caseof the switchgear apparatus 10, in particular fitted in a suitablehousing. The detector 74 is connected in conventional manner to meansfor processing information and presenting results, for example anelectronic module already present on the switchgear apparatus 10 towhich a new function is added. Advantageously, the sensor 70 is asdescribed in the documents EP 1,830,162 or EP 1,921,423, with an angularresolution of about 0.2 to 0.5°.

According to a particular embodiment of the method, estimation of thecontact depression is made by the difference between the final angleθ_(final) and the angle of rotation of the rotation shaft at the momentthe contacts come into contact at the time T₀.

Although the invention has been described with reference to contacts 12,14 of a switchgear apparatus 10 with high electrodynamic strength inwhich the opening mechanism implies a large variation of the angularposition of the pole bar 20 for a small variation of the crushingover-travel, it is not limited thereto: other types of switchgearapparatuses, contactors and/or circuit breakers, can be concerned. Ifgearing-down of the double connecting rod and toggle amplifies theangular difference depending on whether the contacts are worn or not, onthe travel of the contacts and on the precision of the detection device70, it is possible to apply the device according to the invention toother actuating mechanisms comprising a rotary part.

According to an alternative embodiment of the invention that is notrepresented, a sensor measures the rotation of the pole cage 62 betweenthe beginning of movement of the pole shaft 20 and the end of travel ofsaid shaft 20. The end of travel of the pole shaft 20 corresponds to theclosed position of the electric contacts.

The invention claimed is:
 1. A method for evaluating the mechanicalperformances of a switchgear device which comprises at least one pole,each pole comprising: a pair of contacts movable with respect to oneanother between an open position and a closed position; a support arm ofa first contact; a support arm drive mechanism comprising: a rotary poleshaft and at least one rod which pivotably couple the drive mechanism tothe support arm, and an energy storage system for moving said arm toplace the main contacts in a closed position; the method comprising:measuring the angle of rotation of the pole shaft during a closingtravel of the contacts; deriving at least two specific values frommeasuring the angle of rotation; comparing said specific values with aspecific initial operating reference value of the switchgear device;identifying the mechanical wear performances of the drive mechanism bycomparing the specific values obtained with the operating referencevalue; determining on a variation curve of the angle of rotation versustime, a first specific value equal to a first time necessary to reach afirst inflection point corresponding to the moment when the pole shaftreaches a maximum speed of rotation; determining a second specific valueequal to a second time necessary to reach a point on the variation curvecorresponding to a theoretical final angle of rotation reached when thepair of contacts is in a closed position; calculating the elapsed timebetween said first and second times; and deriving an excess energy levelof the energy storage system of the drive mechanism as a function of thedifference between the value of the calculated elapsed time and atheoretical value.
 2. The method for evaluating according to claim 1,comprising: determining on the variation curve of the angle of rotationa third specific value corresponding to a time to reach a first localmaximum on the variation curve, said first local maximum correspondingto the maximum angle of rotation reached by the pole shaft in the courseof closing; determining on the variation curve of the angle of rotationa fourth specific value corresponding to a final angle of rotationreached when the pair of movable main contacts is in a closed position;calculating the angular difference between the maximum angle of rotationand the final angle of rotation; the drive mechanism of the pole shaftcomprising a toggle device associated with a trip latch, and deriving alatching state of the toggle device as a function of said angulardifference.
 3. The method for evaluating according to claim 1,comprising determining the angle of rotation of the pole shaft, by arotation sensor one component of which is located on the pole shaft. 4.The method for evaluating according to claim 3, wherein the rotationsensor comprises magnetic means arranged about the axis of rotation ofthe pole shaft, and detection means on the switchgear device, themagnetic means and detection means communicating with each other withoutphysically contacting each other.